Morgan had this. I had an irrigation tool and some blue solution I don't remember what it was. Then I had to put abx ointment in there. Twice a day. Took about a month of irrigation, injected and oral ABX, maybe 6 weeks for it to clear up - she was 10 though so.

Make sure you're keeping her clean too, no sitting in the dirt outside. Morgan used men's boxers for that.